Arthrotomy with synovial biopsy of the carpometacarpal (CMC) joint of the hand, requiring open incision and tissue sampling of the joint lining.

Verified May 8, 2026 · 7 sources ↓

Medicare: $338.69
Total RVUs: 10.14
Global, days: 90
Region: Hand

Drawn from CMSFastrvuAAPCEatonhandEmedny

Documentation requirements

What must appear in the operative or office note to support the claim.

Source · Editorial brief grounded in 7 cited references ↓

Specify the joint by name (carpometacarpal joint) and side (right or left hand) — laterality omissions are a top edit trigger.
Operative note must confirm arthrotomy was performed: incision through capsule, joint entered, synovium visualized and sampled.
Document the clinical indication driving the biopsy — inflammatory arthropathy, suspected synovitis, crystal deposition disease, or other pathology suspected.
Include pathology order or specimen submission documentation to support medical necessity for the tissue sampling.
If multiple joints were biopsied in the same session, document each joint as a discrete operative event with separate descriptions.
Pre-op diagnosis and post-op diagnosis must be recorded; if post-op diagnosis changes, the ICD-10 should reflect the post-procedure finding once pathology returns.

Applicable modifiers

Modifiers commonly billed with this code.

Source · AMA CPT modifier descriptors · CMS NCCI Policy Manual

22 Increased complexity 24 Unrelated E/M during global 25 Significant separate E/M 50 Bilateral procedure 51 Multiple procedures 52 Reduced services 58 Staged or related 59 Distinct service 76 Repeat, same physician 77 Repeat, another physician 78 Unplanned return — related 79 Unrelated during global 80 Assistant surgeon AS PA/NP/CNS assistant LT Left side RT Right side

What this code covers

Source · Editorial summary grounded in 7 cited references ↓

CPT 26100 describes an open arthrotomy of the carpometacarpal joint with excision of a synovial biopsy specimen. The surgeon incises down to the CMC joint, opens the joint capsule, and removes a sample of the synovial lining for pathologic analysis. This is a diagnostic procedure — the primary goal is tissue, not therapeutic joint debridement or drainage.

The code carries a 90-day global period. That means the operative day, the pre-op visit the day before, and all routine post-op management through day 90 are bundled. Any E/M visit in that window for an unrelated condition requires modifier 24; a separately identifiable E/M on the day of surgery requires modifier 25.

For multiple joints biopsied at the same session — for example, both the CMC and a metacarpophalangeal joint — bill 26100 for the CMC and 26105 for the MCP, appending modifier 51 to the secondary code. Document each joint separately in the operative note. If both hands are operated on in the same session, use modifier 50 or laterality modifiers LT/RT per payer preference.

RVU & reimbursement

Component RVUs and Medicare national rate. Actual payment varies by GPCI locality.

Source · CMS Physician Fee Schedule, RVU26A · January 2026

Work RVU	3.7
Practice expense RVU	5.65
Malpractice RVU	0.79
Total RVU	10.14
Medicare national rate	$338.69
Global period	90 days

Payment by site of service

Medicare pays different rates by setting. HOPD typically pays substantially more than ASC for the same procedure.

Source · CMS OPPS Addendum B·ASC HCPCS payment rates·2026

Setting	Medicare rate (national)
Office (PFS non-facility) Procedure performed in physician's office	$338.69
HOPD (APC 5113) Hospital outpatient department	$3,342.87
ASC (PI A2) Ambulatory surgical center (freestanding)	$1,644.87

Common denial reasons

The recurring reasons claims for CPT 26100 get rejected.

Source · Editorial brief grounded in CMS NCCI edits, AAOS coding appeals, and cited references ↓

Laterality missing — claim submitted without LT or RT modifier when payer requires it, triggering a no-pay edit.
Medical necessity not established — diagnosis code doesn't support an open synovial biopsy when less invasive approaches were available and undocumented as inadequate.
Global period conflict — post-op E/M billed within the 90-day global without modifier 24 appended for an unrelated condition.
Unbundling error — 26070 (arthrotomy with exploration/drainage) billed same-day at the same joint when 26100 already includes the arthrotomy component.
Pathology not ordered or not documented — payer recoupment when specimen submission is absent from the record, calling the biopsy claim into question.

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01Can 26100 and 26070 be billed together for the same joint in the same session?

No. 26070 (arthrotomy with exploration, drainage, or foreign body removal) and 26100 (arthrotomy with biopsy) both include the arthrotomy at the CMC joint. Billing both for the same joint same-day is an unbundling error. Bill only the code that reflects what was actually done.

02If the surgeon biopsied both the CMC and the MCP joint in the same session, how do you bill?

Bill 26100 for the carpometacarpal joint and 26105 for the metacarpophalangeal joint. Append modifier 51 to 26105 as the secondary procedure. Document each joint as a distinct operative event in the note.

03What ICD-10 codes pair well with 26100 for medical necessity?

Common supporting diagnoses include M06.84 (rheumatoid arthritis, hand), M12.241 (villonodular synovitis, hand), M25.241 (effusion, CMC joint), and M79.891 (other specified soft tissue disorders of hand). The diagnosis should reflect why an open biopsy was needed rather than aspiration or needle biopsy.

04Does the 90-day global period mean no office visits can be billed for 90 days?

Routine post-op visits related to the surgery are bundled and cannot be billed separately. An E/M for a new or unrelated problem during the 90-day global is billable with modifier 24. A separate E/M on the day of surgery for a distinct decision-making reason requires modifier 25.

05Is modifier 50 or LT/RT preferred for bilateral CMC joint biopsies?

Payer-dependent. Medicare and many commercial payers accept modifier 50 on a single line. Some Medicaid programs and workers' comp payers require separate line items with LT and RT. Verify the payer's bilateral billing policy before submission to avoid split-claim edits.

06When would modifier 22 apply to 26100?

Modifier 22 is appropriate when the procedure required substantially increased physician work — for example, dense adhesions from prior surgery, severe deformity, or unusual anatomic complexity that significantly extended operative time. The operative note must document the specific factors that made the case harder than typical, and additional supporting documentation should accompany the claim.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira's AI scribe captures joint name, laterality, approach description, capsulotomy detail, and specimen disposition from the surgeon's dictation in real time. It flags operative notes that reference 'the joint' without naming carpometacarpal or specifying side — the two omissions that trigger laterality edits and medical necessity denials most often. Pathology submission intent is also pulled from dictation so the coder knows to cross-check the specimen log before billing.

See how Mira captures CPT 26100 documentation